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<a name="Runtime-Options"></a>
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<a name="Influencing-runtime-behavior"></a>
<h3 class="section">2.8 Influencing runtime behavior</h3>
<a name="index-options_002c-runtime"></a>

<p>These options affect the runtime behavior of programs compiled with GNU Fortran.
</p>
<dl compact="compact">
<dd><a name="index-fconvert_003dconversion"></a>
</dd>
<dt><code>-fconvert=<var>conversion</var></code></dt>
<dd><p>Specify the representation of data for unformatted files.  Valid
values for conversion on most systems are: &lsquo;<samp>native</samp>&rsquo;, the default;
&lsquo;<samp>swap</samp>&rsquo;, swap between big- and little-endian; &lsquo;<samp>big-endian</samp>&rsquo;, use
big-endian representation for unformatted files; &lsquo;<samp>little-endian</samp>&rsquo;, use
little-endian representation for unformatted files.
</p>
<p>On POWER systems which suppport <samp>-mabi=ieeelongdouble</samp>,
there are additional options, which can be combined with others with
commas.  Those are
</p><ul class="no-bullet">
<li><!-- /@w --> <samp>-fconvert=r16_ieee</samp> Use IEEE 128-bit format for
<code>REAL(KIND=16)</code>.
</li><li><!-- /@w --> <samp>-fconvert=r16_ibm</samp> Use IBM long double format for
<code>REAL(KIND=16)</code>.
</li></ul>

<p><em>This option has an effect only when used in the main program.
The <code>CONVERT</code> specifier and the GFORTRAN_CONVERT_UNIT environment
variable override the default specified by <samp>-fconvert</samp>.</em>
</p>
<a name="index-frecord_002dmarker_003dlength"></a>
</dd>
<dt><code>-frecord-marker=<var>length</var></code></dt>
<dd><p>Specify the length of record markers for unformatted files.
Valid values for <var>length</var> are 4 and 8.  Default is 4.
<em>This is different from previous versions of <code>gfortran</code></em>,
which specified a default record marker length of 8 on most
systems.  If you want to read or write files compatible
with earlier versions of <code>gfortran</code>, use <samp>-frecord-marker=8</samp>.
</p>
<a name="index-fmax_002dsubrecord_002dlength_003dlength"></a>
</dd>
<dt><code>-fmax-subrecord-length=<var>length</var></code></dt>
<dd><p>Specify the maximum length for a subrecord.  The maximum permitted
value for length is 2147483639, which is also the default.  Only
really useful for use by the gfortran testsuite.
</p>
<a name="index-fsign_002dzero"></a>
</dd>
<dt><code>-fsign-zero</code></dt>
<dd><p>When enabled, floating point numbers of value zero with the sign bit set
are written as negative number in formatted output and treated as
negative in the <code>SIGN</code> intrinsic.  <samp>-fno-sign-zero</samp> does not
print the negative sign of zero values (or values rounded to zero for I/O)
and regards zero as positive number in the <code>SIGN</code> intrinsic for
compatibility with Fortran 77. The default is <samp>-fsign-zero</samp>.
</p></dd>
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